[Python-Dev] Generated Bytecode ... (original) (raw)

R. David Murray rdmurray at bitdance.com
Thu Oct 22 13:56:53 EDT 2015

On Thu, 22 Oct 2015 17:02:48 -0000, Brett Cannon <brett at python.org> wrote:

On Thu, 22 Oct 2015 at 09:37 Stéphane Wirtel <stephane at wirtel.be> wrote:

> Hi all, > > When we compile a python script > > # test.py > if 0: > x = 1 > > python -mdis test.py > > There is no byte code for the condition. > > So my question is, the byte code generator removes the unused functions, > variables etc…, is it right? > Technically the peepholer removes the dead branch, but since the peepholer is run on all bytecode you can't avoid it.

There's an issue (http://bugs.python.org/issue2506) for being able to disable all optimizations (that Ned Batchelder, among others, would really like to see happen :). Raymond rejected it as not being worthwhile.

I still agree with Ned and others that there should, just on principle, be a way to disable all optimizations. Most (all?) compilers have such a feature, for debugging reasons if nothing else. We even have a way to spell it in the generated byte code files now (opt-0). But, someone would have to champion it and write a patch proposal.

--David

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